This invention relates generally to solenoid actuated valves of the type having a fluid pressure-operated diaphragm to control movement of a valve disc between open and closed positions. More specifically, this invention relates to an improved solenoid actuated valve designed to maintain a minimum or substantially zero pressure differential across the diaphragm in both the open and closed positions of the valve, while providing adjustable selection of fluid flow rate through the valve.
Solenoid actuated valves are generally known in the art for use in opening and closing a valve member or head to correspondingly permit or prevent flow of a fluid such as water along a flow line or conduit. In this regard, solenoid actuated valves commonly include a pressure-operated resilient diaphragm supporting the valve head mounted centrally thereon for movement between the open and closed positions. One side of the diaphragm is exposed to a control chamber adapted to be filled with fluid under pressure obtained typically by bleed flow from the valve inlet, to maintain the diaphragm and valve head in the closed position. A solenoid unit is actuatable to open a vent path to relieve pressure within the control chamber, and thereby permit the fluid pressure at the valve inlet to displace the valve head and/or diaphragm to the open position. Denergization of the solenoid unit recloses the vent path, resulting in pressure build-up in the control chamber to return the diaphragm and valve head to the closed position. Solenoid actuated valves of this general type are used in a wide variety of fluid flow control situations, such as irrigation systems and the like.
In one configuration, the diaphragm and valve head are arranged to expose the valve head in the closed position to elevated fluid pressure at the valve inlet, with a bleed port permitting fluid flow through the valve head to the control chamber. However, this configuration undesirably exposes the resilient diaphragm to a substantial pressure differential when the valve is closed, typically for prolonged time periods between short intervals when the valve is opened. In the event of diaphragm failure attributable to this pressure exposure, the valve will fail in the open position and substantial fluid leakage and/or loss may occur.
In an alternative configuration, the diaphragm is exposed on both sides to the fluid inlet pressure when the valve is closed, thereby substantially balancing the pressures across the diaphragm in the closed condition. When the valve is opened upon venting of the control chamber, however, the diaphragm is again exposed to a substantial fluid pressure differential. To avoid premature diaphragm failure as a result of this pressure differential exposure, the diaphragm has been designed to incorporate substantial structural reinforcement throughout most or all of the diaphragm surface area. Alternately, a rigid backstop structure is provided to support and retain the diaphragm in the open position. Structural reinforcement of the diaphragm undesirably increases the complexity and cost of the valve, whereas the use of rigid backstop structures is incompatible with adjustable setting of the valve head for different selected fluid flow rates through the open valve. In this regard, variable selection of the valve flow rate may be particularly desirable in some operating environments, such as in an irrigation system application wherein generally balanced flow rates to different irrigation zones may be required.
There exists, therefore, a significant need for an improved solenoid actuated valve which minimizes or eliminates fluid pressure differentials across a pressure-operated diaphragm in both the open and closed positions of the valve, while additionally permitting effective regulation of valve fluid flow rate. The present invention fulfills these needs and provides further related advantages.